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It doesn’t happen very often anymore,
but the other day we actually
had a power outage. During
a good hour and a half, nothing
electrical worked, other than the (now
essential) flashlight. And you know what
I noticed?
The silence.
Understand, this is a quiet neighborhood.
The busy streets are within an easy
walk, but the sound of tires and motors
pretty much dies out before it makes it
over. At night it can get downright eerie,
if only because in this modern age we
aren’t used to quiet. Still, quiet is only
relative, as I rediscovered during that
period without power. Suddenly it was
really quiet.
Background noise creeps up on you.
In any household, the refrigerator is
a major noisemaker, rumbling when
it’s running, emitting soft little creaks
and groans when it’s not. In winter,
even “quiet” heating, such a baseboard
heater, emits noise. And if you ever let
them install a high-efficiency burner
on your oil furnace, you’ll discover that
the efficiency is not the only thing that’s
high. As for summertime, if you have air
conditioning…
But there’s more. Around here, the
sound system is always on, but even if it
weren’t it would never really be off. Electronic
devices don’t switch off anymore,
they go into “standby” mode. Television
sets have done that for years; if the TV
were really switched off, it wouldn’t
respond when you hit the power button
on the remote . Computers also get left
on 24/7 by many users. And for a growing
number of people, the computer is
the sound system.
The result is a soft, diffused background
field of 60 Hz (our power line
frequency), radiated by ubiquitous power
transformers. Often, it isn’t even that
soft.
I’ve always found that 60 Hz sound
field disturbing, and it’s a relief when
I can get away from it. The 50 Hz
frequency used in much of the world is
scarcely better, and it is just as audible.
Some countries once had 25 Hz current
72 ULTRA HIGH FIDELITY Magazine
State of the Art
by Gerard Rejskind
(parts of Toronto had it until the 1950’s),
but the low frequency required transformers
with fearsome amounts of iron.
We could go the other way and adopt a
very high frequency that is outside the
range of human hearing, but then the
signal would get into everything. You
might as well be living inside a radio
transmitter.
The gradual buildup of electronic
noise is not trivial, either. Consider this.
When the loudness decibel scale was set
up, in a quieter age, zero decibels was
defined as the loudness of the softest
sound that the human ear can reliably
distinguish (a noise half that loud would
be at -3 dB). It would be nice, then, if we
could keep a nice quiet background level
of, say, -1 dB.
Am I dreaming? You bet. Use a sensitive
sound pressure level meter, and
you’ll discover that the actual quiescent
loudness, when the fridge and the heating
are at rest, and if you don’t live next
to a freeway interchange or a fire station,
is more like 40 dB. How loud is that? It
may seem quiet by modern standards,
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but it is in fact ten thousand times louder
than the threshold of hearing! But of
course, that ambient noise is constant,
so we don’t hear it. Not until the power
shuts down.
For music listeners, this noise level
presents an obvious problem. Let us say
that the loudest sound you will hear at
an acoustic concert (no amplification,
no microphones, but expensive tickets)
is 105 dB. The difference between that
and the ambient noise in your “quiet”
home is 65 dB. That’s not bad, but it’s
easy to see that it is quite a lot less than
the 90 dB or so of dynamic range of a
Compact Disc, and much less than the
noise level of SACD or DVD-Audio.
Indeed, it is less than the dynamic range
you can attain with a turntable.
Even so, I’m using extreme figures
here. A lot of people, even those with
good systems, listen at a maximum level
closer to 95 dB. And lots of homes have
ambient noise that is over 50 dB. The
available dynamic range is then just
45 dB. This means that if you set the
volume so that the peaks are comfortable,
you’ll actually miss entire passages,
because they can be as much as 20 dB
(one hundred times!) below the noise.
It’s not surprising that we get frequent
mail asking for tips on soundproofing:
for keeping out the sounds of the fridge,
the furnace, the lawn mowers and leaf
blowers, the traffic, and of course the
neighbors. If you are building a room
whose main purpose is music listening,
you will certainly want to do all you can
to keep noise out.
But you need to be aware that among
today’s noisemakers are the very components
you will be installing in that room:
amplifiers, CD players, television sets,
and more. They produce music, yes, but
they also produce the noise that masks
their own music.
It’s ironic that many of us use cones
and other isolation devices to keep vibrations
from affecting our audio equipment.
In many cases, the equipment
itself is the major vibration source. The
more of it you have, the more your music
will blend into a grey sonic fog.